1. Field of the Invention
This invention relates to a magnetic device. More particularly, the present invention relates to a magnetic device using a magnetic field generating device and a physical characteristic measurement device thereof for measuring physical and chemical characteristics of an object by affecting the magnetic field applied to a refrigerated magnetic body or to the magnetic device in which a refrigerated magnetic body is magnetized.
2. Discussion of the Background
A bulk-shaped superconductor as a high-powered bulk magnet has been studied.
For example, an application device and a magnetizing method of a superconductor bulk magnet have been disclosed in the following publications. Japanese Patent Laid-Open Publication No. H11-283822 discloses a superconductor magnetic device, which refrigerates a superconductor by a cryogenic refrigerator and magnetizes the superconductor by energizing a magnetizing coil with a pulse electric current to create a superconductor bulk magnet. Japanese Patent Laid-Open Publication No. 2000-277333 discloses a method for creating a superconductor bulk magnet by magnetizing the superconductor by energizing the coil with a pulse electric current under the condition that a ferromagnetic body is provided adjacent to the superconductor.
Further, the lower the temperature, the more improved the performance of the superconductor is in acquiring a magnetic field for externally generating the magnetic field (i.e., acquisition magnetic field performance) according to the foregoing known devices. Thus, the superconductor is refrigerated to a lower temperature using a cooling mechanism such as a cryogenic refrigerator for achieving a high powered superconductor bulk magnet.
In particular, according to the magnetic device disclosed in the Japanese Patent Laid-Open Publication No. H11-283822, because this known device includes a structure for generating the magnetic field at a predetermined position, a distance between a cold head of the cryogenic refrigerator and a superconductor to be magnetized is elongated. Thus, it is difficult to directly refrigerate the superconductor with a cryogenic refrigerator. With respect to this construction, the superconductor is refrigerated by connecting the cold head of the cryogenic refrigerator via a cold head extension portion formed with a material having a high thermal conductivity such as copper.
The pulse magnetization method by energizing the magnetizing coil with the pulse electric current has been adopted as a simple magnetizing method for a superconductor. To increase the performance of the magnetization, as disclosed in the Japanese Patent Laid-Open Publication No. 2000-277333, a yoke including a ferromagnetic body is provided adjacent to the superconductor and the magnetization is performed by refrigerating the superconductor and the yoke together with a cryogenic refrigerator.
Notwithstanding, because the known magnetic devices disclosed in the Japanese Patent Laid-Open Publication Nos. H11-283822 and 2000-277333 include a cold head copper extension portion that has a high thermal conductivity, a sizable eddy current is induced at the cold head extension portion when the pulse magnetic field is applied. When the eddy current is generated, the cold head extension portion presses against the cold head, resulting in damage to the cyrogenic refrigerator.
Further, in a cooling mechanism having a cold head supported by a tube portion, the tube portion is buckled due to the generation of the eddy current. The damage of the tube portion not only spoils the function of the cryogenic refrigerator, but a high-pressure gas in the cryogenic refrigerator is also exhausted.